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  1. #21
    Eugen Mezei's Avatar
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    Thank you all for your answers.

    Now I have a doubt: Is ignition by spark or by fuse in comercial bulbs?

    Well... I intend to use aluminium foil as this is what I have handy. (I eat a lot of chocolate.) Of course magnesium foil or zirconium wire would be better, but where to get? I also think some of the big bulbs avaible from manufacturers were filled with aluminium foil.

    Yes, I will coat the glass. I think laquer for wood or metal will suffice, I will try to get a thick one.

    Final achievment of the experiment should be bigger bulbs that the ones avaible comercially. But I will begin with small ones out of safety considerations.

    Steve, is that wire wool the thing used to clean/scrub hardened residues from dishes?

  2. #22

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    Chemical Primer compounds?

    If I remember correctly, Class M flashbulbs utilized a chemical on the ignition electrodes to stabilize/improve ignition. I am not sure what sorts of chemicals may have been used.

    Class F flashbulbs such as the GE Speed Midget (SM) had no metal filaments that burned and the "flash" was all from a Chemical which burned in an oxygen atmosphere.
    Dave

    "She's always out making pictures, She's always out making scenes.
    She's always out the window, When it comes to making Dreams.

    It's all mixed up, It's all mixed up, It's all mixed up."

    From It's All Mixed Up by The Cars

  3. #23

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    "What makes a flashbulb flash? Well, flashbulbs have, placed between their terminals, a piece of tungsten or zirconium filament. This wire is covered with an explosive primer paste. When current is applied, the wire heats up, igniting the paste, which then ignites the tin, aluminum or (in later years) aluminum wire (or wool). An oxygen atmosphere would increase the brilliance of the flash. Some bulbs were also filled with nitrogen gas to actually slow or delay the burn"

    The statement above is from the link below.
    http://www.darklightimagery.net/flashbulbs.html

  4. #24
    holmburgers's Avatar
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    I'm really excited about your project. How will you make the actual glass bulbs?

    I'm (slowly) working on an IR-transmitting coating for flashbulbs (a la GE #5R) and I intend to coat the bulbs in gelatin. Gelatin might be another option over varnish, though varnish would probably be easier; just dip and hang.

  5. #25
    greybeard's Avatar
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    Yes, I will coat the glass. I think laquer for wood or metal will suffice, I will try to get a thick one.

    Not, I sincerely hope, a nitrocellulose lacquer

    Commercial flashbulbs use a very thick layer of plastic, probably cellulose acetate or something similar. They tended to have a very characteristic "toasted" smell when fired.

    You mentioned making large bulbs; if you do, be very careful: as a kid of about eight or nine, I found some of the bulbs which are the size of a 150-watt incandescent, and fired one by touching it to the terminals of a lantern battery. It blistered essentially all of the palm and fingers of my left hand, even though the envelope didn't break and I dropped it more or less instantly. The radiated power, at close range, is awesome.

  6. #26

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    I think you could weld 1/4 inch steel if you had a big enough flashbulb.
    Dave

    "She's always out making pictures, She's always out making scenes.
    She's always out the window, When it comes to making Dreams.

    It's all mixed up, It's all mixed up, It's all mixed up."

    From It's All Mixed Up by The Cars

  7. #27

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    Quote Originally Posted by Eugen Mezei View Post
    Thank you all for your answers.

    Now I have a doubt: Is ignition by spark or by fuse in comercial bulbs?

    Well... I intend to use aluminium foil as this is what I have handy. (I eat a lot of chocolate.) Of course magnesium foil or zirconium wire would be better, but where to get? I also think some of the big bulbs avaible from manufacturers were filled with aluminium foil.
    First of all, ignition was neither by spark or fuse. It was by flame. Essentially, the priming compound caught fire, which ignited the flashbulb.

    Aluminum foil will work fine, but not in the thickness that is sold in stores. The aluminum foil has to be either extremely thin or finely shredded in order for it to ignite. The same goes for magnesium and zirconium, but they're easier to form than aluminum
    "Panic not my child, the Great Yellow Father has your hand"--Larry Dressler

  8. #28
    Eugen Mezei's Avatar
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    So if I understand it correctly the priming compound was ignited by heat and not by a spark. At first I thought the electrolytic condensator was to produce a powerful spark. Thought for heating it would deliver to short of a time energy. Seems this is not the case, correct me if I'm wrong.

    nickrapack's hint with the electric matches was a very good one. I thought myself about something similar before but wasn't shure if this would work. I will try now to build some thin wire coated with black powder. Hope this would make a nice primer.

    For the first experiments I will use a jar or a bottle. The finished product will be glass tubes. These are closed at one end (they are giant test tubes like used in laboratories) and I will put a presumably ceramic plug (or even clay) and run the wires through it.

    I shredded aluminium foil from chocolate as fine as I could (well, I have different broad strips) and hope it will ignite. I seems to me that kitchen foil is somewhat thicker. I only have one bulb filled with foil, an RFT (GDR produced) and for me the foil seems to be not thicker than what I have.

    Beside to build bigger bulbs my idea came from using alu powder in the free (mixed with an oxidant) but this is very impractical for the smoke it generates. So I think I would have better results if the smoke remains closed in the glass.

    Any ideas about preparing oxygen from chemicals? Finally I would do it by electrolysis but for testing I don't want to deal with hydrogen too.

  9. #29
    Eugen Mezei's Avatar
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    Quote Originally Posted by Eugen Mezei View Post
    I will try now to build some thin wire coated with black powder. Hope this would make a nice primer.
    I will also try to mix some Al or maybe Mg powder to the bp.

  10. #30

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    Have you tried this:

    http://www.google.com/patents?q=flash+bulb

    There is some interesting information that can be gleaned from patents.

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